1. Field of the Invention
The present invention relates to an organic light emitting diode having a thin insulating layer, and more particularly, to an organic light emitting diode having a thin insulating layer inserted between its organic emissive layer and the cathode, to thereby improve its light emission efficiency.
2. Discussion of Related Art
FIG. 1 is a cross-sectional view showing the structure of a general organic light emitting diode. Referring to FIG. 1, an anode 2 is formed on a glass substrate 1, and an emissive layer 3 is formed on anode 2. A predetermined pattern of cathode 4 is formed on the emissive layer 3.
In the above-described light emitting diode, electrons are injected from cathode 4 to emissive layer 3, and holes are injected from anode 2 to emissive layer 3. The injected electrons and holes are recombined in emissive layer 3, to emit light. Balanced injection of the electrons and holes improves the light emission efficiency of the diode.
In the conventional light emitting diode, anode 2 is formed of an indium-tin compound, and cathode 4 is formed of aluminum. In this case, the amount of holes injected is much more than that of electrons because the electron injection energy barrier is much higher than the hole injection energy barrier. Thus, the amount of electrons and holes are imbalanced in the emissive layer 3, thereby decreasing the light emission efficiency.
To overcome this dificiency, a material having smaller work function like calcium is used for forming the electrodes in order to increase the injection of electrons. However, calcium is unstable in the air.